Threshold energy release rate

T, To Energy release rate, maximum, threshold Tc Critical energy release rate... 

Figure 9.7 Schematic illustration of relation between strain energy release rate G and delamination crack growth rates as established via tests on standard geometry double cantilever bend and edge notched flexure samples, showing threshold for growth at G and static fracture at G = Gic-...

This latter is eompared with the strain energy release rate threshold AGth-If AG > AGth the analysis starts (or it continues is the increment is not the first) otherwise the analysis is stopped. 

In a plot of of (square of the threshold stresses for crack propagation) versus reciprocal crack length a a distinct lower bound was found which defined a critical energy release rate Gj whereas Gi initially decreases with temperature it becomes independent of temperature at T > where Tc roughly corresponds to the Tg of PMMA in the particular environment. 

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